Stage boxes and audio snakes do essentially the same task for us on the set. They allow us to use a single cable to extend the inputs/outputs of our mixing board closer to the actual set or stage. As you can imagine, this can be very convenient and a lot easier than having to run several independent mic cables.
At the mixer end, we have a fantail of XLR male connectors, duly numbered, that connect to the XLR mic inputs on our board. In addition, we may have some 1/4-inch TRS plugs that can go into the Aux Sends or Monitor Outs.
At the "stage" end, there would be another fantail ("snake") or a metal "stage box" with female XLR mic inputs along with 1/4-inch jacks (Aux Sends or Monitor Outs).
This makes it a simple matter to run short XLR cables to the actors or musicians, along with headphone, IFB, or monitor outputs. Even a boom operator could plug their "duplex line" into the stage box to send audio from their shotgun mic and receive a headphone signal.
Equipment Emporium sells the popular Little Bro 6x2 stage boxes made by HOSA. These units feature six XLR connections and two 1/4-inch jacks. The 30 foot version costs $110 and a fifty foot version is only $144.
For large venues, such as concerts or major broadcast studios, we often use a variation of this concept known as a digital snake (or digital stage box, to be more precise). Instead of running a thick, analog multi-strand cable from the mixing console to the stage area -- we simply deploy a single CAT-5 ethernet cable up to 300 feet in length. An AC powered stage box is at the other end, with up to 32 XLR inputs and 16 monitor outputs! This box serves as a remote microphone preamp (Analog to Digital converter) and offers 48vPhantom powering for the mics.
Digital snakes are not inexpensive, and require either a matching digital mixing board (such as the Roland series) or a mating digital to analog breakout box to connect up with your mixing board.